#include <cstdio>
#include <algorithm>
#include <cmath>
using namespace std;
int main(void){
    double a,b,c,l,m,n;
    while(~scanf("%lf%lf%lf%lf%lf%lf",&a,&b,&c,&l,&n,&m)){
        double ans=sqrt((4*a*a*b*b*c*c-a*a*(b*b+c*c-m*m)*(b*b+c*c-m*m)-b*b*(c*c+a*a-n*n)*(c*c+a*a-n*n)-c*c*(a*a+b*b-l*l)*(a*a+b*b-l*l)+(a*a+b*b-l*l)*(b*b+c*c-m*m)*(c*c+a*a-n*n)))/12;
        printf("%.4lf\n",ans);
    }
    return 0;
}